Sensing device for slice delivery to fourdrinier wire



Sept. 2, 1969 s. M. SALOMON 3,464,887

SENSING DEVICE FOR SLICE DELIVERY TO FOURDRINIER WIRE med sept. 2v. 1965 United States Patent O U.S. Cl. 162-263 9 Claims ABSTRACT OF THE DISCLOSURE A transducer producing an electrical signal as a function of flow stream velocity for positioning in the slice flow stream of :a headbox and being movable both vertically and horizontally relative to the slice stream.

This invention relates generally to a sensing device for a slice delivery from a headbox and more particularly to a System for sensing and measuring characteristics of a headbox slice delivery at various points along the delivery path. The present invention has particular application in the papermaking field wherein the slice delivery from a headbox must be maintained uniform at all points along the slice delivery path to provide uniform characteristics of the resultant paper web.

The primary function of a headbox is to deliver paper stock onto a Fourdrinier wire which is evenly distributed across the wire, well disbursed, and delivered at a steady velocity. These results are difficult to attain, and in practice the actual process of supplying the paper stock to the wire is complicated by problems introduced by the particular design of the headboxes. Even distribution of the stock across the wire, disbursement of the constituents of the stock, and the slice delivery velocity, if not maintained within prescribed limits, will produce defects in the resultant paper web.

For instance, friction between the walls of a headbox and the stock flowing -therefrom will cause a decrease in the velocity of the stock delivery at the ends of the slice. A difference in velocity or flow pressure across the width vof the slice delivery will result in defects in the resultant paper web. The edges may be reduced in Ithickness as compared to the center portions of the paper web which may cause other difficulties in subsequent operations, such as during the drying and rolling processes. Uniformity of paper thickness, however, is of utmost importance to the customer, since weak spots will often result in holes and tears.

Therefore, a need exists for a system for sensing and measuring the characteristics of a headbox slice delivery at various points along the delivery path and recording such characteristics for comparison of the conditions eX- istent in the slice delivery across the width thereof. In such a system, however, in order to sense the characteristics of a slice delivery, a sensor is required which may interfere with the flow pattern and characteristcs of the slice delivery. Therefore, it is necessary that such a sensing device have an appropriate configuration such that it will not interfere substantially with the ow pattern from the headbox.

In order for a sensor to provide a minimum of interference with the flow pattern and characteristics of the slice delivery stream, the sensor must be relatively small sized and of relatively light weight sothat it can be inserted and withdrawn from the slice delivery stream in a relatively short time. However, the sensor and support structure therefor must have sufficient strength in the direction of the forces exerted thereon so as to eliminate any possibility of vibration during its introduction into the slice delivery stream.

ICC

Therefore, it is an object of the present invention to provide a system for measuring a characteristic of a slice delivery stream from a headbox.

Still another object of the present invention resides in the-provision of a sensing device which will have a minimum adverse affect on the flow pattern of a slice delivery stream from a headbox.

vStill another object of the present invention is to provide a system for measuring characteristics of a slice delivery stream which is movable along the flow path of the stream to provide an indication of the characteristics at various stations of the ow path.

`Yet another object of the present invention resides in the provision of a relatively light weight and relatively small sized sensor which can be inserted and withdrawn from the slice delivery stream from a headbox in a relatively short time.

Yet another object of the present invention resides in the provision of a relatively light weight and small sized sensor having a support structure for positioning the sensor in a slice delivery stream which will eliminate vibrations and other adverse affects upon the sensor from theforces of the stream thereon.

Still another object of the present invention resides in the provision of a slice delivery stream sensor which Will provide a minimum adverse affect on the ow pattern of the stream by virtue of the aerodynamic configuration thereof while possessing sufficient strength to resist forces of the stream tending to produce vibrations and other adverse affects thereon.

These and other objects, features and advantages of the present invention will be more fully realized and understood from the following detailed description when taken in conjunction with the accompanying drawings wherein:

.FIGURE l is a schematic showing of the sensing dcvice of the present invention illustrated in the slice delivery stream from a headbox;

FIGURE 2 is a perspective view partially broken away of the sensing device of the present invention;

FIGURE 3 is a sectional view taken along lines III-III of FIGURE 2;

FIGURE 4 is a schematic diagram of the electrical circuit and indicating device in cooperation with the sensng device of the present invention; and

FIGURE 5 is a schematic perspective view of a mechanism for moving the sensor.

Like reference numerals throughout the various views of the -drawing are intended to designate the same or similar structures.

With reference to the drawing, and in particular to FIGURE l, there is shown schematically a sensing device 10 positioned in a slice delivery stream indicated generally by the reference numeral 12 from a headbox 14. The headbox 14 generally includes a stock inlet conduit 16, a plurality of rectifier rolls 18, and an adjustable slice 20 positioned at an outlet 22. A Fourdrinier wire 24 is supported beneath the outlet 22 on a roll 26 which rotates in the direction of the arrow indicated thereon. The Fourdrinier wire 24 receives the slice delivery stream 12 thereon which is formed into a paper web as indicated at 28.

The sensing device 10 is disposed for being inserted and withdrawn from the slice delivery stream 12 as indicated by the arrow 30. This vertical movement of the sensing device 10 with respect to the slice delivery stream 12 can be performed by any means well known in the art. As shown in FIGURE 5, the sensing device may be moved by a piston 30a having a piston rod 30h, and movable Within a closed cylinder 30C. Compressed air is supplied to either end of the cylinder through flexible air lines 30d and 30e to lower 'or raise the strut 36. The flexible air lines permit the cylinder 30a` to be moved along the headbox 14. The sensing device is better illustrated in FIGURES 2 and 3.

The sensor 10 as illustrated in FIGURES 2 and 3 includes a pressure transducer 32 mounted in one end of a housing generally designated with the reference numeral 34. The housing 34 is supported in the slice delivery stream 12 by means of a strut 36. The strut 36 is connected to suitable means for moving the sensor 10 vertically as indicated by the arrow 30 in FIGURE 1. Such suitable means may comprise, for instance, an air cylinder having its actuating arm secured to the strut 36 and having the cylinder thereof fixedly mounted with respect to the headbox 14. It is to be understood, however, that any suitable structure may be employed for moving the sensor 10 vertically with respect to the slice delivery stream 12 as above stated. It is preferable that such structures, however, be relatively fast acting to permit immediate insertion and withdrawal of the sensor 10 into the slice delivery stream 12. Therefore, the sensor 10 may be inserted into the slice delivery stream 12 and instantaneously withdrawn therefrom so as to provide a minimum amount of disturbance to the ow of stock onto the Wire 24.

In addition, the sensor 10 may be mounted for horizontal movement as indicated by the arrow 38. For instance, the stmt 36 may be mounted on a screw-threaded rod 38a driven by a positioning motor M such that the sensor 10 can be moved horizontally across the outlet 22 of the headbox 14. The rod 38a will carry a traveling nut 38b which supports the cylinder 30C. Rotation of the rod in either direction will move the strut 36 in either direction along the headbox. Simultaneous horizontal and vertical movement of the strut can be accomplished by rotation of the rod 38a at the same time as movement of the piston 30a. In this manner, the pressure characteristics of the slice delivery stream 12 can be sensed at various stations along the length of the slice delivery outlet 22. A comparison of pressure readings taken at various stations along the length of the outlet 22 will provide an indication of the undesirable disturbances created in the slice delivery stream 12 by the headbox 14 and its associated structures. In addition to the adverse affects on the slice delivery stream 12 from the headbox 14, there will exist a variation in the basis weight of the paper stock exiting from the outlet 22. This basis weight variation is caused by various factors and can be determined by a measurement of the pressure exerted on a transducer at the outlet 22.

As shown in FIGURES 2 and 3, the housing 34 is formed of a head portion 40 and a tail portion 42 in threaded engagement with one another. The head portion 40 includes a central aperture 44 therethrough which is slightly enlarged as indicated at 46 to provide a shoulder 48.

The tail portion 42 of the housing 34 is threadedly engaged to the head portion 40 as indicated by the reference numeral 50. A cavity 52 is provided in the tail portion 42 and forms a shoulder 54 adjacent thereto. The transducer 32 includes an enlarged portion 56 which abuts on one side thereof with the shoulder 48 and on the other side thereof with the shoulder 54 when the head portion 40 is threaded into engagement with the tail portion 42. The tail portion 42 also includes a conduit hole 58 extending therethrough and in alignment with a conduit hole 60 extending through the center of the strut 36. The conduit holes 58, 60 extend to the cavity 52 for receiving a cable 62 therein carrying appropriate wires which are connected to the transducer 32 and to appropriate recording elements.

As shown in FIGURE 3, one end of the transducer 32 is ush with one end of the aperture 44 so as to place the transducer in position for direct contact with the slice delivery stream 12.

As more clearly illustrated in FIGURE 2, the head portion 40 and the tail portion 42 each have a circular lateral cross-section and a teardrop longitudinal crosssection for providing an aerodynamic configuration to the slice delivery stream 12. The end of the transducer 32, which is provided in the cavity 52, the aperture 44, and flush with the end of the aperture 44, complements the teardrop configuration of the housing 34. The strut 36 has a teardrop lateral cross-section and, as illustrated in FIGURE 3, the longitudinal axis of the strut 36 is displaced from the longitudinal axis of the housing by an acute angle to provide a more streamlined shaped to the slice delivery stream 12. The rounded ends of the housing 34 and the strut 36 face into the delivery stream 12 to provide a minimum adverse affect thereon.

The transducer 32 of the present invention is of relatively small size and weight having an exposed surface at the one end of the housing 34 which has a diameter of .25 inch. The transducer 32 is of the flush diaphragm pressure type and occupies a volume less than 0.05 cubic inch and weighs approximately one-tenth of an ounce. This small size and relatively light transducer allows irnmediate insertion and Withdrawal of the unit into and out of the slice delivery stream 12. As can be readily appreciated from FIGURES '2 and 3, the housing 34 and strut 36 are relatively inexible to forces exerted on the rounded end of the portion 40. Therefore, when the slice delivery stream 12 is directed against the exposed face of the transducer 32, substantially no vibrations will occur with respect to the housing 34 supporting the transducer 32. Therefore, pressure measurements derived from the transducer 32 will not be affected by fluctuations and vibrations of the supporting structure.

It can be readily appreciated that the transducer 32 can provide an indication not only of pressure in the slice delivery stream 12, but Will provide an indication of the speed of the stream 12 and the basis Weight of the stock therein.

Contained Within the conductor 62 are conductors for applying a source of voltage to the transducer 32 and for providing a signal from the transducer 32 to a recording instrument. A circuit for providing such an indication is illustrated schematically in FIGURE 4 wherein a voltage is applied to a pair of terminals 64 and 66. A Ibalanced bridge circuit generally indicated with the reference numeral 68 is connected at input terminals thereof to the terminals 64, 66 and contains in one leg thereof a resistive unbonded strain gage such as indicated by the reference numeral 70 and forming a part of the transducer 32. A recorder 72 is connected across output terminals of the bridge circuit 68 and provides an indication of any unbalance of the resistance in the circuit. Therefore, since the value of resistance of the resistor 70 changes in proportion to the pressure exerted on the eX- posed face of the transducer 32, an indication of such change will be recorded on the recording device 72. A resistor 74 is provided for balancing the entire circuit and a limiting resistor 76 is connected from substantially mid-point on an adjustable arm of the resistor 74 to one of the output terminals of the bridge 68.

The recording device 72 can provide an indication of either pressure, velocity, or basis weight of the stock in comparison to either horizontal movement or distance of the transducer 10 from one end of the headbox 14 or in comparison to a time basis. Therefore, the recording device 72 may be of the strip recording type as illustrated and either pressure, velocity, or basis Weight may be recorded thereon in the Y direction while horizontal movement or distance of the sensor 10 from one end of the headbox 14 or time may be recorded along an X direction thereof. Terminals 78 and 80 are provided for driving the recording device 72 in accordance with horizontal movement or displacement of the sensor 10 or in accordance with lapse of time. In this manner, a comparison of readings at the various stations across the outlet 22 can be derived from the recording device 72. If desired, the recording device 72 can be replaced by a tape recorder or other similar recording device for providing a permanent record of the readings obtained from the sensor 10.

I claim as my invention:

1. A device for measuring paper stock ow from a headbox onto a traveling paper web forming surface comprising,

a transducer having a pressure sensitive area and producing an electrical output signal as a function of flow velocity,

a relatively small housing supporting said transducer being of a size to generate substantially no disturbance in the flow characteristic of a stock stream emerging from a headbox slice,

a support for said housing for mounting the housing on a headbox in the stock stream between the slice opening and web forming surface,

and a movable positioning means between the support and the housing for moving said housing to predetermined locations in said stock stream.

2. A device for measuring paper stock flow from a headbox onto a traveling paper web forming surface in accordance with claim 1 wherein said housing comprises means forming a cavity in one end thereof with said transducer mounted in the cavity facing the oncoming stock stream.

3. A device for measuring paper stock ow from a headbox onto a traveling paper web forming surface in accordance with claim 2 wherein said transducer is mounted flush with said one end of said housing.

4. A device for measuring paper stock flow from a headbox onto a traveling paper web forming surface in accordance with claim 1 wherein said housing is aerodynamically shaped and oriented in the direction of the stock stream flow to offer minimum ow resistance.

5. A device for measuring paper stock flow from a headbox onto a traveling paper web forming surface in accordance with claim 1 wherein said support comprises a strut having an aerodynamic configuration.

6. A device for measuring paper stock flow from a headbox onto a traveling paper web forming surface in accordance with claim 1 wherein said positioning means further includes means for moving said housing simultaneously vertically and horizontally.

7. A device for measuring paper stock flow from a headbox onto a travelling paper web forming surface in accordance with claim 5 wherein said housing comprises a longitudinal axis and is constructed and arranged so as to have a circular lateral cross-section and a teardrop longitudinal cross-section and wherein said strut is constructed and arranged so as to have a teardrop lateral cross-section as well as a longitudinal axis displaced at an acute angle to the longitudinal axis of said housing so that a minimum amount of disturbance is created in said stream.

8. A device for measuring paper stock flow from a headbox onto a travelling paper web forming surface in accordance with claim 1 wherein said positioning means further comprises means for moving said housing vertically into and out of the stock stream.

9. A device for measuring paper stock flow from a headbox onto a travelling paper web forming surface in accordance with claim 1 wherein said positioning means further comprises means for moving said housing horizontally along a line parallel to the stock stream.

References Cited UNITED STATES PATENTS 2,769,929 11/ 1956 Hardway. 3,078,709 2/ 1963 Clark 324-71 X S. LEON BASHORE, Primary Examiner U.S. Cl. X.R. 'I3-53, 194; 162-198; 23S-151.31, 151.34; 324-71 

